1. Field of the Invention
The invention has to do with methods for ultrasonically determining thickness and characterstics of an interior part at various points along the length of a coextending outer part.
2. Description of the Prior Art
Ultrasonic measuring of the type here concerned is old and well known. Transducer and transceiver instrumentation for accomplishing such measuring can be purchased commercially. Accessory instrumentation for blocking out certain unwanted signals is available for use with the transceiver and provision is made for plugging in a strip chart recorder so thicknesses and characteristics of the interior part can be visually observed and the chart can be kept as a permanent record. Moreover, it is common for the transceiver to be equipped with a cathode ray tube (CRT) so that the signals can be displayed as they are received. However, in instances in which strength differences between diverse signals are very great, with the one critical signal being very weak and others being very strong, interference by extraneous signals can become so diffuse and pervasive as to destroy the taking of any effective measurements.
Such a situation has heretofore prevented the use of this otherwise common ultrasonic technique for monitoring an ultrasonic signal from the interface between an extruded tube of zirconium metal and a coextruded tubular liner of a very similar zirconium metal and similarly monitoring an ultrasonic signal from the interior surface of the lined tube, from which signals thicknesses and characteristics of the liner are calculated within the instrumentation, and provided as output, based on timing the travel of the ultrasonic wave between such signals, all in customary manner.
It is important in the nuclear energy industry utilizing such coextruded zirconium tubes for containing nuclear fuel that the thickness of the liner be substantially uniform along the length of the tube and that measuring such thickness be possible short of destruction of the tube by cutting through it at intervals. Utilizing well known ultrasonic techniques would be a solution but has heretofore been regarded as impossible from a practical standpoint.